Curing of diisocyanate-modified polyester



Patented Dec. 9, 1947 CURING OF DIISOCYANATE-MODIFIED POLYESTER WillFurness. Lyle E. Pen-ins, and Walter Fairbairn Smith. Blackley.Manchester, England, assignors to Imperial Chemical Industries Limited,acorporation of Great Britain No Drawing. Application March 14.1944,Serial In Great Britain February 10,

2 Claims. (Cl. 260-43) This invention relates to improvements in thecuring of polymeric organic materials more especially in the curing oforganic diisocyanatemodified polyesters or polyester-amides.

Polyesters and polyester-amides are obtained by heating a glycol and/oran amino alcohol with a dibaslc carboxylic acid. optionally in thepresence oi. one or more additional ingredients, namely a diamine, anaminocarboxylic acid or a hydroxycarboxylic acid; alternatively, one ormore of the ingredients may be used in the form of the correspondingesteror amide-forming derivatives. In order to obtain linear polymers,the amounts of the various ingredients are selected so that there arepresent approximately chemically equivalent proportions of theircomplementary ester-forming groups and also of their complementaryamide-forming groups, if amide-forming ingredients are used. The linearpolyesters or the linear polyester-amides which may be obtained in thisway are usually soft, waxy materials with a relatively low molecularweight. It has been proposed to convert these soft, waxy, low molecularweight linear polymers into tough polymers of considerably highermolecular weight by heating them with small proportions of an organicdiisocyanate, for example ethylene diisocyanate, trimethylenediisocyanate, tetramethylene diisocyanate, hexamethylene, diisocyanate,decamethylene diisocyanate, m-phenylene diisocyanate and naphthalenediisocy-anates. Furthermore, it has been proposed so to treat such lowmolecular weight linear polymers which have been obtained by reactingthe several ingredients in such proportions that there is present in thereaction mixture a small excess of an alcoholic hydroxyl-containingingredient over and above that theoretically required. If justsuflicient of the isocyanate to react with the end groups in the lowmolecular weight linear polymers is used in their conversion into thehigh molecular weight polymers, there are obtained linear polymers whichcan be extruded into colddrawable filaments. However, if greaterproportions of the isocyanate are used, there are obtained tough,rubbery, partly cross-linked, high molecular weight polymers whichcannot be extruded into cold-drawable filaments. Whatever proportions ofthe isocyanate are reacted with the linear polyesters orpolyester-amides, we shall refer to the resulting polymers collectivelyas organic isocyanate modified polyesters or polyester-amides, and it iswith these modified polymers that the present invention is concerned.

decamethylene glycol, 1:12-octaclecanediol, and pentaglycol; aliphaticor aromatic aminoalcohols having at least one hydrogen atom attached tothe amino nitrogen atom and preferably containing a saturated aliphaticchain of at least "two carbon atoms separating the amino andbymonocarboxylic acids or their amide-forming derivatives, for example,G-aminocaproic acid or its amide-forming derivative caprolactam,9-aminononanoic, ll-aminoundecanoic and 12-aminostearic acids.

The low molecular weight polymers are made by heating the selectedingredients at polymerizing temperatures, usually in the absence of airor oxygen, in the first place usually in the presence of water, andlater under conditions whereby water is removed from the reactionmixture. When using a diamine as one of the ingredients, it isconvenient to use it as the corresponding diammonium salt formed fromsome of the dibasic carb'oxylic acid to be used.

The low molecular weight, linear polyesters or polyester-amides areconverted into the high molecular weight polymers by mixing them, forexample by stirring, milling or kneading, with the organic diisocyanateand then simultane-.

ously and/0r subsequently heating the mixture, for example to atemperature of to 200 C., for a period of about 10 to 120 minutes. Up toabout 10% and usually between 3% and 7% of the isocyanate isused. Thepolymers modified with diisocyanates may be polyesters having norecurring intralinear carbonamide groups or they may be polyester-amideshaving a ratio of intralinear ester to carbonamide groups of 1:1, as inthe case of polyesters made from dibasic acids and ethanolamine orhaving a higher ratio of ester to amide groups.

In the specification of British application No. 13,204/41 (U. S. SerialNo. 466,356, filed November 20, 1942) it has been proposed to cureorganic diisocyanate modified polyesters or polyesteramides by heatingthese in the presence of formaldehyde or of a formaldehyde-liberatingsubstance and in the presence or absence of materials which function ascuring catalysts, namely, acids, acid anhydrides or acid-reacting salts.As formaldehyde-liberating substances there are mentioned thereinpolymerides of formaldehyde, such as paraformaldehyde andtrioxane;compounds containing a reactive methylol group or groups such asdimethyloiurea, trimethylolmelamine, hexamethylolmelamine,diphenylolpropane tetraalcohol, methylolchloracetamide,methylolstearamide and N-methylol-p-toluenesulphonamide; ethers ofcompounds containing a reactive methyloi methylolurea dimethyl ether,dimethylolurea dibutyl ether and N:N'-dimethyloluron dimethyl ether(Chemical Abstracts, 30, (1986), 5944-5); 1:2-glycol methylene ether,di-(p-hydroxyethyl) formal and hexamethylene tetramine-zinc chloridecomplexes. as well as thermo-hardening phenol-formaldehyde condensationproducts derived by alkaline condensation from phenols with more thantwo free positions ortho and para to the phenolic hydroxyl group.

In the specification of British application No. 7392/42 (U. S. SerialNo. 484,444, filed May 25,

- 1943) it has been proposed to cure organic diisocyanate modifiedpolyesters or polyesteramides in a manner similar to that of the abovementioned prior proposal, but differing in that there are used, ascuring catalysts, materials which are substantially neutral and remainso during temperatures obtaining during milling or other pre-curingoperation but which develop acidity at temperatures attained duringcuring.

The present invention is directed to improving the properties of therubber-like cured materials obtainable in accordance with these priorproposals.

We have found that, when a proportion of a thermo-hardeningphenol-formaldehyde condensation product derived from a phenol with morethan two free positions ortho and para to the phenolic hydroxyl group orgroups is brought into admixture with an organic diisocyanate modifiedpolyester or polyester-amide and, as a curing agent, a non-phenolicformaldehyde-liberating substance and also a curing catalyst, then thecured materials obtainable therefrom are endowed with improved physicalproperties, more especially with improved heat-ageing properties.

Thus, according to the present invention, in

' the process of curing organic diisocyanate modifled polyesters orpolyester-amide in the pres-' ence of a non-phenolicformaldehyde-liberating substance and of a curing catalyst of the kindhereinbefore described, we provide the improvement which compriseseffecting the curing also in the presence of a thermo-hardeningphenolformaldehyde condensation product derived from a phenol with morethan two free positions ortho and para to the phenolic hydroxyl group orgroups.

As nonphenolic formaldehyde-liberating substances, that is to say,formaldehyde-liberating substances which are not derived from phenols.there may be used those materials of this kind described in thespecification of British appl cation No. 13,204/41 (U. S. Serial No.466,356, filed Nov. 20, 1942).

As curing catalysts there may be used. for example. or anic acids suchas formic, glvcollic,

, oxalic, succinic, maleic, adipic. tartaric, salicylic,

anthranil c. phth-alic. citric and tannic acids; in-

or an c acids such as boric and phosphoric acds; I acid anhydrides suchas phthallc Qif maleic anhygroup or groups sch as di-- which developacidity under curing conditionssuch as, butadiene sulphone,2:3-dimethylbutadiene sulphone, butadiene tetrabromide, styrenedibromide, acetylene tetrabromide, tribromohydroquinone, l-bromo-2-naphthoi, 1:6- dibromo-2-naphthol, l :4 6-tribromo-2-naphthol, 24-dibrom0- l-naphthol, methyl or p-dibromopropionate. p chloroethyl-a2fldibromoisobutyrate, ethyl a-bromopropionate, phenyltrichioroacetate, a a B-trichloropropionitrile, trichloroacetamide,trichloroacetyldiethylamide, N- trichloroacetylanilide, N:N'-di-(trichloroacetyl) methylenediamine, NzN' di (trichloroacetyl).ethylenedi-amine, interpolymers of asymmetrical dichloroethylene andvinyl chloride, and chloranil (tetrachloro-p-benzoquinone).

As the thermo-hardening phenol-formaldehyde condensation products theremay be used, for example, those derived from phenol, m-cresol,diphenylolpropane, 1:3:5-xylenol, resorcinol or mixtures containing atleast one such phenol, for example, cresylic acid containing 40-50% byweight of m-cresol, or the products obtained by condensing suchphenol-formaldehyde resins or their components with monohydric alcoholsboiling above C. Preferably the condensation products are resins, forexample those obtained by condensing together, in presence of sodiumhydroxide, phenol or 1:3:5-xylenol or diphenylolpropane or m-cresol withaqueous formaldehyde, or by condensing diphenylolpropane andformaldehyde with butanol or cyclohexanol.

As well as the ingredients already mentioned one or more additionalingredients may also be used. These include non-basic fillers, forexample carbon black, clay, asbestos, blanc fixe and mica; other plasticmaterials for example, natural or synthetic rubbers, vulcanisedvegetable oils, dark substitute, white substitute, a comarone resin,wood rosin and pitch; detackifying agents, for'example, stearic acid,paraffin wax, oleic acid and lauric acid; plasticisers, for example,tricresyl phosphate, dibutyl phthalate, butylphthalyl butyl glycollateand N-alkyltoluene sulphonamides; stabilisers or antioxidants, forexample, hydroquinone N:N'- hexamethylene-bis o hydroxybenzamide, N-phenyl-a-naphthylamine, N-phenyl-fi-naphthylamine and a:a:-bis(2-hydroxy-3:5- dimethylphenyi-butane. Small quantities of non-basic pigments,for-example from 1-3% by weight such as are customarily used in rubbertechnology may also be used to impart colour. Small amounts ofacid-accepting materials may be used to obviate or minimise scorching.This expedient is described in Buist et al. U. S. application Serial No.522,801, filed Feb. 17, 1944.

The invention is carried into practical effect in the manner describedin the above mentioned specifications. Usually the several ingredientsare mixed together, conveniently on arubber mill, at a temperature belowwhich there is an apprec able tendency for curing to take place on themill, 1. e. below about 70 C., the mix is removed from the mill, ifdesired, formed into shapes or spread or calendered onto a substrate.for example, onto the surface of a fabric, and then cured by heating,for example, in a press or mould or in hot a r, for periods of not moreone hour at temperatures of about e means By using thermo-hardeningphenol-formalde hyde condensation products, usually in amounts varyingfrom about 5'to 20 parts per 100 parts by weight of the organicdiisocyanate modified polyester or polyester-amide, in accordance withthis invention cured rubber-like materials with improved properties areobtained. For instance,

the improved materials may have a better tensile strength, an increasedmodulus, an increased hardness. greater resistance to softening by0115,,

and so forth. There is always an outstanding improvement in heat-ageingproperties. This im- 7 provement is so marked that, as may be seen fromcomparative measurements of hardness after periods of exposure toelevated temperatures in the presence of air or oils. the use of thethermohardening condensation-products in accordance with the inventionsubstantially reduces or, in many cases. entirely prevents degradationof the cured materials on exposure to high temperatures.

The invention is illustrated but not limited by the following examples,in which the parts are expressed by'weight.

Example 1 Mixes of the following components are made up on a two-rollrubber mill andthen cured in a mould under hydraulic pressure at atemperature of 141 C. for minutes:

Diisocyanate modified polyester-amide i Hydroquinone. Carbon blackParaformaldebyde Styrene dibromide Alkaline condensedphenol-formaldehyde resin Some of the properties of the curedmaterialsare as follows:

Shore hardness at 25 C B. S. I. Hardness at 25 C Resilience at 50 C Theimprovement in ageing properties resulting from the presence of thephenol-formaldehyde resin is shown in the following table:

B. S'. I. Hardness at 25 C. Ageing in Air at 120 C.

5:08 row FIQSON l Too soft to test.

Similar results are obtained by using 7 instead of 3 parts ofparaformaldehyde and 1.5 parts of phthalic anhydride in place of the 2parts of styrene dibromide.

The alkaline condensed phenol-formaldehyde resin used in this example isobtained by refluxing for 15 minutes a mixture of 100 parts of phenol,124 parts of 37% aqueous formaldehyde solution and a little sodiumhydroxide solution.

Example 2 Mixes of the following-components are made -up on a two-rollrubber mill and then cured in a Styrene dibromide .1 1:

mould under hydraulic pressure at a temperature of C. for 30 minutes.

Dissocyanate modified polyester-amide 1 Hydro quinone L Carbon black.Stearic acid Paraiormaldehyd i-bromo-z-naphtholButylated-diphenylolpropanc-formaldehyde resin.

Some of the properties oi the cured materials are as follows:

Tensile strength, KgJcm. 164 Elongation at break. percent 487 433Modulus at 300% extension 82 82 Resilience at 50 C 58.0 60. 1 Shorehardness at 25 C. 55 53 B. S. I. hardness at 25 C. 59 61 The improvementin ageing properties resulting from the presence of thebutylated-diphenylolpropane-formaldehyde resin is shown in the followingtable:

B. B. I. hardness at 25 C.

Ageing in air at 120 C.

42 days 1 Too soft to test.

the distillate and returned to the reaction vessel throughout thedistillation. 18 parts of phthalic anhydride are then added to thecontents of the reaction vessel-and the azeotropic distillation iscontinued as before for a further 3 hours. The resin is isolated byremoving the organic liquids in vacuo.

Example 3 Mixes of the following components are made up on a two-rollrubber mill and then cured in a mould under hydraulic pressure at atemperature of 141 C. for 15 minutes:

'Diisoeyanate modified polyester-amide v. 1 Hydroquinona. Carbon back.-. Stearic acid Parniormaldebyde 2*.9 catamaransDiphenylolpropane-forrnaldehyde res n Alkaline condensedphenol-formaldehyde resin (as used in Example 1) 5 assesses;

7 The improvement in ageing properties resultin from the presence of theresins is shown in the following table:

used in this example is made by heating 333 parts of diphenylolpropane,420 parts of 36% aqueous formaldehyde solution and 8.4 parts of 50%aqueous sodium hydroxide solution under nitrogen at 95 C. for 42minutes, cooling to 70 C. and maintaining this temperature for 4% hours.The batch is then neutralised with hydrochloric acid, washed with waterand dried in vacuo.

Example 4 Mixes of the following components are made up on a two-rollrubber mill and then cured in a mould under hydraulic pressure at atemperature of 125 C. for 30 minutes:

Diisocyanote modified polyester-amide 100 100 Hydroquinone 2 2 Carbonblack. 60 60 Stearic acid 0. 5 0.5 Parelormaldehvde. 5. 0 5. 0 Styrenedibromide 1.5 1.5 Alkaline Condensed phenol-formaldehyde resin I Some ofthe properties of the cured materials are as follows:

Tensile strength, Kg/cm. 84 138 Elongation ill hrcuk, percent 173 267Shore-hardness at C 65 61 Shore hardness at 25 C. after ageing [orrefluxing temperature for one hour a mixture of 47 parts of phenol, 123parts of 36.8% aqueous formaldehyde solution and 4.5 parts of 32%aqueous sodium hydroxide, cooling the reaction mass and neutralising itwith hydrochloric acid, separating the product, washing it with waterand then drying it in vacuo.

The diisocyanate modified polyester-amide used in the above examples ismade according to the recipe of Example 7 of the specification ofBritish application No. 13, 04/41 (U. .S. Serial No. 466,356, filed Nov.20, 1942) and is obtained as follows: 127.75 parts of adipic acid, 42.25parts of ethylene glycol and 13.6 parts of monoethanolamineare heatedtogether under carbon dioxide to 190 C. during seventeen hours and themixture is then subjected to continuous azeotropic distillation withxylene at 180-190 C. for twentytwo hours. Most of the xylene is thenremoved by 8 distillation at 185 C. A pale yellow syrup with a meltviscosity of 68 poises at 75 C. and an acid value of 9.6 mm. KOH per gm.is obtained. This syrup slowly hardens to a soft, cream-colored wax.

This wax is treated in a steam heated internal mixer at 145 C. with 45%of hexamethylene diisocyanate (added in three portions at fifteen minuteintervals). The so obtained diisocyanate modified polyester-amide is asoft, rubber-like material which does not harden on standing.

Example 5 Mixes of the following components are made up on a two-rollrubber mill and then cured in a mould under hydraulic pressure at atemperature of 141 C. for 15 minutes:

Diisocyanate modified polyester-amide l00 Hydroquinone 2 2 60 60 0. 6 0.5 Parainrmaldehyd l0 l0 l. b l. 6 Diphenyiolpropane-i'ormuldei1yderesinmade as described in Example 3 20 Some of the physical propertiesof the cured materials are as follows:

Tensile strength, Kg./crn.. 210 204 Elongation at. break, percent. 620373 Modulus at 300% extension-.. 90 152 Shore hardness at 25 C 50 54Shore hardness at 25 C. after ageing for 35 days in oil at 70 C 36 68The presence of the resin results in the production of a cured materialwith considerably improved resistance to softening by hot oil. withbetter heat-ageing properties and with an increased modulus.

The diisocyanate modified polyester amide used in this example is madeaccording to the recipe of Example 1 of the specification of BritishApp'lication No. 13,204/41 (U. S. Serial No. 466,356, filed Nov. 20,1942) and is obtained as follows:

469 parts of ethylene glycol, 1314 parts of adipic acid, 91.5 parts ofmonoethanolamine and 200 parts of water are mixed together and heatedwith stirring whilst a stream of nitrogen is passed over the heatedmixture, the temperature being raised during two hours to 170 C. Themixture is maintained at 170 C. for seven hours, after which time thedistillation of water ceases. The temperature is raised to ISO-190 C.,the blanket of nitrogen being still maintained, and xylene is addedcontinuously and distilled to remove all traces of water as awater-xylene azeotropic binary. After 36 hours the xylene distillate isclear, indicating the removal of all traces of the water. The mixture isnow heated for 3 hours at 180-190 C. in vacuo (20 mm./Hg) to remove thexylene. There is thus obtained a thick syrup which graduallycrystallises on standing and which has an acid value of 16 mgm. KOH per.gm. 1318 parts of this syrup are put into a steam heated internal-mixerand the temperature is raised to -140 C. 61 parts of hexamethylenediisocyanate are then added, in small portions during one hour, whilstthe temperature of the mixer is gradually raised to C. The syrupgradually thickens to a tough, rubbery mass. The mixer is cooled to100130 C. and the so-obtained diisocyanate modified polyester-amide isremoved.

We claim:

1. In the process of curing the reaction prodsubsequent to compounding,the mass is subuct of a hydrocarbon diisocyanate and a low molecularweight linear polymer with 3 to parts of paraformaydehyde per 100 partsof the said reaction product and an acid curing catalyst, the said lowmolecular weight linear polymer being of the class consisting ofpolyesters containing recurring intralinear carboxylic ester groups andpolyester-amides containing recurring intralinear carboxylic estergroups and recurring intralinear carbonanzide groups, the ratio of saidester groups to said carbonamide groups being at least 1:1, the stepwhich comprises effecting the compounding in the presence of 5 to partsper hundred parts by weight of the said reaction product of athermal-hardening phenol-formaldehyde condensation product derived froma phenol with 20 2 2 2 10 aldehyde to the said thermal-hardeningphenolformaldehyde condensation product being no more than 1:1.

2. The process of claim 1, characterized in that,

jected to a temperature of C. to C. whereby to effect curing.

WILL FURNESS.

LYLE E. PERKINS.

WALTER FAIRBAIRN SMITH.

REFERENCES cI'rEn The following references are of record in the file ofthis patent:

UNITED STATES, PATENTS Number Name Date 2,282,827 Rothrock May 12, 19422,333,917 Christ et al Nov. 9,1943

Schlack May 6, 1941 2,177,637 Coflman Oct. 31, 1939

